Systemic infection with Herpes bovis virus 2 evokes a biphasic immune response in the mouse

We evaluated the effects of systemic infection by Herpes bovis virus 2 (HBV-2) on a murine experimental system. We provide evidence that such infection is lethal for the immunocompromised but not for the immunocompetent mouse in which a biphasic immune response is elicited. In particular, 1 day post-infection, we observed a rapid transient depression induced by the virus, as documented by a decrease in peripheral leukocyte counts, mitogenic spleen cell response and resistance to a secondary microbial challenge. Later, HBV-2 infection boosted cytokine secretion and enhanced antimicrobial and antitumoral activities by the splenic district. In conclusion, our experimental model discloses some immunological aspects underlying the complex host-virus interaction.

The herpes simplex virus type 1 strain 17+ gamma 34.5 deletion mutant 1716 is avirulent in SCID mice

Laboratory animal models are important tools for the identification of avirulent herpes simplex virus type 1 (HSV-1) strains which have potential for use in humans as vaccine strains or gene therapy vectors. We have studied an HSV-1 17+ variant, 1716, that has a deletion in the gamma 34.5 gene and which replicates poorly in the footpads of mice and is unable to grow in the mouse central nervous system or dorsal root ganglia (DRG) of the peripheral nervous system following peripheral inoculation. However, 1716 is known to be capable of establishing latent infections in the DRG of mice. Here we show that 1716 is avirulent after ocular infection and has low virulence after intracranial inoculation in SCID mice. Since SCID mice are much more sensitive to HSV-1 infection than immunocompetent mice, our results clearly demonstrate the drastically reduced virulence of the variant 1716 and provide additional support for the hypothesis that this variant would be avirulent in humans.

Fatal disseminated herpesvirus infection with hepatitis. A peritoneal fluid cytologic warning

A 19-year-old man died of a disseminated herpesvirus infection. Microscopic examination of a peritoneal fluid specimen revealed cellular changes characteristic of a herpetic process, and an autopsy confirmed widespread herpes simplex virus type II infection. Viral infections may be diagnosed by cytologic examination of body fluid specimens.

Gastrointestinal invasion by herpes simplex virus type 1 inoculated cutaneously into the immunosuppressed mice

The pathogenesis of infection in mice with herpes simplex virus type 1 (HSV-1) strain 7401H was studied. Mice immunosuppressed by intraperitoneal injection of cyclophosphamide were inoculated cutaneously into the flank with the virus and developed severe zosteriform skin lesions. All of them died within 2 weeks after the infection, while most of the normal mice survived the viral infection with healing of the lesions. In the gastrointestinal tract of the immunosuppressed mice, macroscopic abnormalities were frequently observed, and infectious viruses were detected on days 7 to 9. The viruses were also detectable in the dorsal root ganglia and the spinal cord of thoracolumbar area on days 5 to 7, and in the celiac plexus on day 7. However, no viruses were detected in the blood. Immunohistological examination of the gastrointestinal tract revealed that the viral antigens were localized in Auerbach's myenteric plexus. These results suggest that HSV-1 inoculated into the flank skin invaded the gastrointestinal tract via the nervous system, which gastrointestinal involvement might possibly have caused the death of the mice.

Lethal infections in patients with hematological malignancies

The hospital files of 410 patients with hematological malignancy treated at our clinic between 1977 and 1990 were reviewed to determine the importance of infections as a cause of death. The total number of infections was 203 (49.5%). A microbiologically documented infection was detected in 27.3%, a clinically documented infection in 9.5% and a possible infection in 12.7% of the patients. Gram-positive bacteria were responsible for 25.9%, gram-negative bacteria for 31.3%, anaerobic bacteria for 2.7%, viruses for 4.5% and fungi for 25.9% of the microbiologically documented infections. Of 29 systemic fungal infections only 2 were diagnosed before the patients died. The remaining diagnoses rested on autopsy findings. Empiric antifungal therapy was introduced in 1983; still, 74.2% of systemic fungal infections in 1977-1990 were detected after 1982. Patients with a verified infection had statistically significantly higher CRP concentrations than patients who died of other causes (152 mg/l vs. 117.5 mg/l, p = 0.018). We conclude that infection is a significant cause of death in patients with these diseases. The number of systemic fungal infections is increasing, despite the widespread use of antifungal medication and thus better diagnostic methods and more effective treatment are needed.

Distribution of herpes simplex virus DNA in the brains of human long-term survivors of encephalitis

We have examined the distribution of type 1 herpes simplex virus (HSV-1) DNA in the brains of 8 humans surviving for between 4 months and 17 years after acute encephalitis. Histological examination showed neuronal loss and gliosis largely confined to the temporal and frontal lobes, typical of HSV-1 encephalitis. There was a widespread persistent inflammatory infiltrate, present in both the cerebrum and brainstem. Viral DNA was detected in paraffin sections of formalin-fixed paraffin-embedded autopsy brain by use of the polymerase chain reaction to amplify a fragment of the HSV-1 thymidine kinase gene. HSV-1 DNA was amplified from the cerebrum in 6/8 cases and from the brainstem in 4/8 cases. These findings suggest the possibility that HSV-1 may persist within the human central nervous system after acute herpes simplex encephalitis. The distribution of the viral DNA correlates better with that of the persistent inflammatory infiltrate than with the destructive lesions of the acute encephalitis.

Neonatal herpes simplex virus infections: pathogenesis and therapy

Neonatal herpes simplex virus (HSV) infections are of increasing incidence in North America, now occurring at a rate of approximately one in 3,500 to one in 5,000 deliveries per year. Disease manifests as one of three forms; namely, infection: localized to the skin, eye and mouth (SEM), encephalitis (CNS), or disseminated disease. With the advent of antiviral therapy, it has become possible to decrease mortality and improve morbidity for babies suffering from infection. Advances in antiviral therapy have allowed for prevention of disease progression beyond states of SEM involvement. Furthermore, life threatening infections of the CNS or of multiple organs, have mortality with either acyclovir or vidarabine therapy. Now approximately 15% (CNS) and 50% (disseminated disease) of babies die from neonatal HSV disease. The results of ongoing studies in the United States will summarize the pathogenesis and treatment of neonatal HSV infection.

Acyclovir monotherapy versus acyclovir plus beta-interferon in focal viral encephalitis in children

Severe focal viral encephalitis is most commonly caused by herpes simplex virus (HSV), but other viruses may act as etiologic agents as well. Acyclovir (ACV) is the standard therapy for HSV encephalitis, but the mortality of 28% and defect healing rate of about 35% are still unsatisfactory. Furthermore, ACV has virtually no effect on other pathogens of viral encephalitis, except for varicella-zoster virus (VZV). It is well known that beta-interferon (beta-IFN) has a broad antiviral spectrum, and it has been demonstrated in vitro that beta-IFN in combination with acyclovir has synergistic inhibitory effects on HSV. To investigate if the combination of ACV with and without beta-IFN might also be of significance for the treatment of severe viral encephalitis, we performed a retrospective study. A case record form was sent to all 278 West German children's hospitals. The response rate was 78%. A total of 301 patients were reported, of whom 214 received specific antiviral therapy with either ACV alone (n = 179) or ACV plus beta-IFN (n = 35). No overall differences between ACV monotherapy and the combination therapy were observed. However, in a subgroup of 41 patients (ACV n = 30, ACV plus beta-IFN n = 11) who had low-density areas of the temporal lobes on cranial computed tomography scans, compatible with severe focal encephalitis, sequelae due to defect formation and mortality were significantly (p = 0.014) reduced in patients who had received combination therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Outcome of herpes simplex virus type 2 infection in guinea pigs

Factors that influence the outcome of genital herpes simplex virus (HSV) infection were explored in a guinea pig model. The viral inoculum required to establish infection in 50% of animals (ID50) was similar for inbred (strain 2) and outbred (Hartley) guinea pigs. However, the viral inoculum required to produce clinical disease in 50% of the animals (CD50) was 10 times greater for strain 2 compared to Hartley animals. HSV infection of both inbred and outbred animals was more likely to result in death of weanling than adult animals. The duration and severity of genital disease and the magnitude of vaginal viral replication were similar for strain 2 and Hartley animals in both young and adult animals. The lethal dose for 50% of animals (LD50) was 100-fold greater than the CD50 for Hartley animals, but the LD50 and the CD50 were equal in strain 2 guinea pigs. Viral cultures of homogenized neural tissues from infected animals revealed that HSV ascended to the level of the temporal cortex in strain 2 guinea pigs while virus was never recovered above the lumbar spinal cord in Hartley animals. Endogenous peripheral blood mononuclear cell-mediated cytolytic activity against HSV-infected targets was greater prior to HSV inoculation in survivors compared to animals that died. A fatal outcome of genital HSV-2 may relate to the failure to limit CNS viral replication. Death is more common among guinea pigs that have low endogenous HSV-directed natural killer activity, such as occurs among strain 2 and young animals whether inbred or outbred.

Recombinant interleukin-1 alpha, interleukin-2 and M-CSF-1 enhance the survival of newborn C57BL/6 mice inoculated intraperitoneally with a lethal dose of herpes simplex virus-1

Recombinant Interleukin-1 alpha (IL-1 alpha), Interleukin-2 (IL-2) and recombinant macrophage colony-stimulating factor-1 (M-CSF-1) as well as combinations of IL-2 and M-CSF-1 were studied for their ability to protect seven-day-old C57BL/6 mice against HSV-1 infection. Treatment of the mice with IL-2, M-CSF-1 or combinations of IL-2 and M-CSF-1 significantly increased survival rates. Treatment with IL-1 alpha (10 U and 100 U/mouse) was most effective in protection against HSV-1, resulting in significantly increased survival rates more than four times greater than the survival rate of the infected control group.

Prognostic factors in childhood acute encephalitis

We have studied the prognostic factors in 462 children, from 1 month to 16 years old, with acute encephalitis. Death occurred in 2.8% patients, 6.7% were severely damaged and 90.5% were cured with no or only minor sequelae. The risk of death or severe damage in patients less than 1 year of age was 5.0-fold (95% confidence limits, 2.2 to 11.6; P less than 0.001) greater than that of older children. When compared with those children whose level of consciousness had been normal before admission, children who had been disoriented before admission had a 3.9-fold (1.1 to 14.3, P less than 0.05) risk and those who had been unconscious had a 25.4-fold (7.3 to 88.1, P less than 0.001) greater risk of death or severe damage. The risk of death or severe damage in patients with herpes simplex virus encephalitis was 11.7-fold (3.8 to 35.8, P less than 0.001) and in patients with Mycoplasma pneumoniae encephalitis it was 7.0-fold (2.6 to 18.7, P less than 0.001) that of other children. All patients with none of the above mentioned risk factors were cured without any major sequelae. We conclude that specific attention should be paid to the youngest patients, especially to those with an impaired level of consciousness, and all available measures should be focused on early detection of herpes simplex virus or M. pneumoniae infection.

Selective depletion of liver and splenic macrophages using liposomes encapsulating the drug dichloromethylene diphosphonate: effects on antimicrobial resistance

The current results provide direct evidence for a role of tissue macrophages (M phi) in natural immunity and support the use of immunomodulators to enhance antiviral resistance in immunocompromised individuals. In this study, macrophages (M phi) in the spleen and liver were eliminated by intravenous (i.v.) injection of the drug dichloromethylene diphosphonate (DMDP) encapsulated in liposomes. The effect of this depletion system on peritoneal M phi, peripheral blood leukocytes, splenic natural killer (NK) activity, and natural and immunomodulator-induced host resistance was then assessed. Barrier-maintained CD-1 female mice were inoculated i.v. either with DMDP liposomes, free liposomes (containing no DMDP), or saline on day -2 or on days -3 and -1 before cell population analysis or infection. Single or double treatment with DMDP liposomes had no effect on peritoneal M phi as indicated by no changes in total number, differential counts, or ectoenzyme patterns. Double treatment with DMDP liposomes caused a marked leukocytosis in blood, primarily of lymphocytes and polymorphonuclear leukocytes (PMN), and a transient depression of spontaneous and interferon-inducible splenic NK activity. The effects on host resistance to i.v. infection with Listeria monocytogenes or herpes simplex virus type 2 (HSV-2) indicated that i.v. treatment with DMDP liposomes significantly reduced natural resistance to these microorganisms as evidenced by increased mortality and decreased median survival time. When DMDP liposomes-treated mice were given the immunomodulator maleic anhydride divinyl ether copolymer (MVE-2) intraperitoneally the day before infection with HSV-2, the immunosuppressive effect of DMDP liposomes treatment was significantly reversed.

Induction of encephalitis in SJL mice by intranasal infection with herpes simplex virus type 1: a possible model of herpes simplex encephalitis in humans

Herpes simplex encephalitis (HSE) is characterized by focal lesions of hemorrhage and necrosis, primarily in the inferior temporal lobe. Since immunosuppressed patients with HSE lack the focal inflammatory changes and temporal lobe localization, it has been suggested that the immune system participates in the pathogenesis of HSE. Evaluation of this hypothesis has been impeded by the lack of an immunologically defined animal model that resembles the human disease. Toward this end, 10 strains of inbred mice were infected intranasally with a neurovirulent clinical isolate of herpes simplex virus type 1. Most mice died without localizing signs of disease in the central nervous system. However, a significant number of SJL mice had a pattern of encephalitis highly reminiscent of that described in humans. To our knowledge, this is the first murine model that faithfully mimics this human disease, and thus it affords the opportunity to study the immunopathogenesis of HSE.

Predictors of morbidity and mortality in neonates with herpes simplex virus infections. The National Institute of Allergy and Infectious Diseases Collaborative Antiviral Study Group

BACKGROUND

In a controlled trial comparing acyclovir with vidarabine in the treatment of neonatal herpes simplex virus (HSV) infection, we found no significant difference between the treatments in adjusted mortality and morbidity. Hence, we sought to define for the entire cohort (n = 202) the clinical characteristics that best predicted the eventual outcome in these neonates.

METHODS

Data were gathered prospectively at 27 centers between 1981 and 1988 in infants less than one month of age who had virologically confirmed HSV infection. We examined the outcomes by multivariate analyses of 24 variables. Disease was classified in one of three categories based on the extent of the involvement at entry into the trial: infection confined to skin, eyes, or mouth; encephalitis; or disseminated infection.

RESULTS AND CONCLUSIONS

There were no deaths among the 85 infants with localized HSV infection. The mortality rate was significantly higher in the 46 neonates with disseminated infection (57 percent) than in the 71 with encephalitis (15 percent). In addition, the risk of death was increased in neonates who were in or near coma at entry (relative risk, 5.2), had disseminated intravascular coagulopathy (relative risk, 3.8), or were premature (relative risk, 3.7). In babies with disseminated disease, HSV pneumonitis was also associated with greater mortality (relative risk, 3.6). In the survivors, morbidity was most frequent in infants with encephalitis (relative risk, 4.4), disseminated infection (relative risk, 2.1), seizures (relative risk, 3.0), or infection with HSV type 2 (relative risk, 4.9). With HSV infection limited to the skin, eyes, or mouth, the presence of three or more recurrences of vesicles was associated with an increased risk of neurologic impairment as compared with two or fewer recurrences.

A controlled trial comparing vidarabine with acyclovir in neonatal herpes simplex virus infection. Infectious Diseases Collaborative Antiviral Study Group

BACKGROUND

Despite the use of vidarabine, herpes simplex virus (HSV) infection in neonates continues to be a disease of high morbidity and mortality. We undertook a controlled trial comparing vidarabine with acyclovir for the treatment of neonatal HSV infection.

METHODS

Babies less than one month of age with virologically confirmed HSV infection were randomly and blindly assigned to receive either intravenous vidarabine (30 mg per kilogram of body weight per day; n = 95) or acyclovir (30 mg per kilogram per day; n = 107) for 10 days. Actuarial rates of mortality and morbidity among the survivors after one year were compared overall and according to the extent of the disease at entry into the study (infection confined to the skin, eyes, or mouth; encephalitis; or disseminated disease).

RESULTS

After adjustment for differences between groups in the extent of disease, there was no difference between vidarabine and acyclovir in either morbidity (P = 0.83) or mortality (P = 0.27). None of the 85 babies with disease confined to the skin, eyes, or mouth died. Of the 31 babies in this group who were treated with vidarabine and followed for a year, 88 percent (22 of 25) were judged to be developing normally after one year, as compared with 98 percent (45 of 46) of the 54 treated with acyclovir (95 percent confidence interval for the difference, -4 to 24). For the 71 babies with encephalitis, mortality was 14 percent with vidarabine (5 of 36) and with acyclovir (5 of 35); of the survivors, 43 percent (13 of 30) and 29 percent (8 of 28), respectively, were developing normally after one year (95 percent confidence interval for the difference, -11 to 39). For the 46 babies with disseminated disease, mortality was 50 percent (14 of 28) with vidarabine and 61 percent (11 of 18) with acyclovir (95 percent confidence interval for the difference, -20 to 40); of the survivors, 58 percent (7 of 12) and 60 percent (3 of 5), respectively, were judged to be developing normally after one year (95 percent confidence interval for the difference, -40 to 50). Both medications were without serious toxic effects.

CONCLUSIONS

In this multicenter, randomized, blinded study there were no differences in outcome between vidarabine and acyclovir in the treatment of neonatal HSV infection. The study lacked statistical power to determine whether there were sizable differences within the subgroups of those with localized HSV, encephalitis, or disseminated disease.

A follow-up study of children with neonatal herpes simplex virus infections with particular regard to late nervous disturbances

Forty-five children with neonatal herpes simplex virus (HSV) infection, representing all known cases in the diagnostic records of four virological laboratories within a 15-year period, were followed up. Twelve children had died. Sixteen of the 33 survivors were healthy. Thirteen children had severe disabilities: all of them showed severe mental retardation; moreover, 11 were tetraplegic, one was hemiplegic with hydrocephalus and one had a pronounced behavioural abnormality. Four children had slight to moderate disabilities: one child was mildly mentally retarded and three, although mentally normal, had hemiplegia and delayed speech development, one of them having a learning disorder as well. Of these 17 neurologically impaired children 16 had ophthalmological abnormalities. EEG recordings were made in 29 patients in the neonatal period. They were markedly abnormal in 24 patients, 14 of whom had localized periodic complexes. An abnormal EEG was a bad prognostic sign. The neurological outcome was better in the HSV-1-infected children (10 cases) than in the HSV-2-infected ones (35 cases). Progressive or recurrent encephalitis was strongly suspected in two preterm children.

[Immunity to tumors induced by herpes simplex virus in hamsters]

Preparations of early herpes simplex virus antigen (VIA) and specific antibodies to it were used to induce active and passive immunity to herpes virus-induced tumors in experimental animals. The results demonstrated the increased resistance of animals to transplantation of tumor cells due to vaccination with VIA-containing preparations. Thus, in VIA-vaccinated animals there was a delay in the development of tumors and the survival time was significantly higher than in the controls. The sera of these animals contained antibodies to VIA in high titres. Experiments with passive immunization also gave encouraging results.

Comparison of antiviral efficacies of 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil (brovavir) and acyclovir against herpes simplex virus type 1 infections in mice

1-beta-D-Arabinofuranosyl-E-5-(2-bromovinyl)uracil (brovavir) and acyclovir were compared for their antiviral effects against herpes simplex virus type 1 (HSV-1) model infections in mice. Both drugs were not toxic to mice when they were administered orally by the same schedule used for therapeutic experiments. Brovavir was less toxic than acyclovir when injected by the intraperitoneal (i.p.) route. Marked efficacies of brovavir by either oral or i.p. administration were demonstrated in both experimental encephalitis and i.p. infection with HSV-1 WT-51 strain. Treatment with brovavir at a dose of 15 or 25 mg/kg twice daily resulted in increasing both survival rate and mean survival time of the infected mice. On the contrary, acyclovir showed only marginal effect against the experimental encephalitis. Survival rates of mice treated with brovavir were higher than those treated with acyclovir at corresponding doses with statistical significance. The superiority of brovavir was also found in the intracerebral infection with strain VR-3, a highly virulent strain for mice. Brovavir, but not acyclovir, at a dose of 200 mg/kg reduced the mortality. Acyclovir, however, were significantly effective in reducing mortality of systemically infected mice by both oral and i.p. administrations. The effective dose of acyclovir was lower than that of brovavir against i.p. infection with strain WT-51. Differences in mortality of strain VR-3-infected mice were statistically significant between acyclovir- and brovavir-treated groups.

Effect of acyl substituents of synthetic lipid A-subunit analogues on their immunomodulating antiviral activity

A chemically synthesized lipid A-subunit analogue, GLA-60, 2-deoxy-4-O-phosphono-2-[(3R)-3-hydroxytetradecanamido]-3-O-[(3R)- 3- tetradecanoyloxytetradecanoyl]-D-glucose, has many of the activities of endotoxin but has little toxicity. Then, compounds with various lengths of acyl side chain of the acyloxyacyl group at the 3-O position of GLA-60 were synthesized and evaluated for interferon (IFN)-inducing activity, natural killer (NK) cell activation and antiviral activity. The compounds with acyl side chains between C8 and C15 exhibited significant antiviral activity (inhibition of pox tail lesion formation in vaccinia virus-infected mice), serum IFN-inducing activity and NK cell activation. However, the compound carrying a C2 or a C16 acyl side chain did not exhibit these activities. The compounds with a C13 or C14 acyl side chain showed strong protective against herpes simplex virus type 1 in cyclophosphamide-immunosuppressed mice.

Herpes simplex virus stromal keratitis is not titer-dependent and does not correlate with neurovirulence

We developed a murine model of ocular herpes simplex virus (HSV) disease which is particularly suited for testing stromal keratitis because most animals show some evidence of infection. Using this model, we characterized the ocular disease patterns caused by ten recent low-passage clinical isolates of HSV-1, as well as those caused by the established laboratory strains HSV-1 KOS and HSV-2 333. Viral strains were evaluated for their ability to cause stromal keratitis, blepharitis, vascularization of the cornea, and mortality. The model was not useful for scoring epithelial keratitis. The ocular disease caused by the recent isolates ranged from very mild disease to severe stromal keratitis. Some of the recent isolates caused disease as severe as the two laboratory strains. A comparison of the virulence characteristics expressed by various HSV strains indicated that the ability to cause stromal disease was correlated with vascularization of the cornea (correlation coefficient = 0.797, P less than 0.001) and was not correlated with the neurovirulence of the strains (correlation coefficient 0.045, P greater than 0.05). The severity of stromal keratitis was not dependent on the amount of inoculum over the range tested and a strain causing severe stromal keratitis caused severe ocular disease even when mixed with a nonstromal strain at ratios of 10:1, 100:1, and 1000:1.

An improved model of recurrent herpetic eye disease in mice

Mice were passively immunized with serum containing antibodies to herpes simplex virus type 1 (HSV-1) before inoculation on the cornea with HSV-1 strain McKrae. After such immunization most mice survived and most had normal eyes. When primary infection had subsided, mice with normal eyes were selected and treated with cyclophosphamide, dexamethasone and UV irradiation of the inoculated eye or UV irradiation alone, to reactivate latent virus. After either treatment mice developed signs of recurrent infection (virus in eyewashings and recurrent corneal and/or lid disease). The incidence of such signs was 17/33 (52%) in mice receiving immunosuppressive drugs and UV irradiation and 19/32 (59%) in mice given UV irradiation alone. In mice treated with either stimulus dendritic or geographic ulceration of the cornea was seen. These closely resembled the herpetic lesions seen in humans. There was good correlation between the pattern and distribution of recurrent corneal disease and the distribution of cells containing virus antigens in corneal epithelial sheets. Again, as in humans, the induction of recurrent infection was found to correlate poorly with a rise in the level of serum neutralizing antibody. In mice treated with UV irradiation alone corneal ulcers healed and the eyes returned to normal. By contrast, in mice given immunosuppressive drugs and UV irradiation, the ulceration became more severe and the eyes became opaque and vascularized. The use of passive immunization has greatly improved our previously reported model of recurrent herpetic eye disease since it has increased the incidence of mice suitable for the induction of recurrent infection and has increased the incidence of such infection.

DNA polymorphism among isolates from multiple sites of a patient with chronic herpes simplex virus, type 1 infection

DNA polymorphisms among independent isolates of herpes simplex virus (HSV) type 1 were studied from a 7-year-old male patient with recurrent infections of the skin and internal organs. In the patient's serum, HSV antibodies could not be detected by complement fixation, enzyme-linked immunosorbent assay (ELISA), or neutralization tests. ELISA tests for the presence of antibodies to human immunodeficiency virus were also negative. One HSV isolate was obtained from mesenteric nodes biopsied in 1983; one from skin in 1984; and three (postmortem) from brain, lungs, and liver in 1985. Restriction enzymes Eco RI, Bgl II, Hind III, Kpn I, and Bam H1 digestion patterns of the five isolates were similar. However, Sal I digests of isolates from skin, mesenteric nodes, lungs, and liver showed variations that were distinct from that of the brain isolate. Although Sal I digests of skin, mesenteric nodes, lungs, and liver isolates share a common variation in lacking F and G, the liver isolate can be further differentiated because of the gain of a restriction site on the H fragment. Thus, the three distinct variants observed were the isolates from brain (variant 1); from skin, mesenteric nodes, and lungs (variant 2); and from liver (variant 3). The fragments involved in variations among these isolates (presence or absence of Sal, G and H) are from the unique short and long regions (invariable regions) of the genome and therefore do not show heterogeneity in size. The extent of variation among these isolates is less than that seen among epidemiologically unrelated strains, suggesting that they originated from a single infecting strain, probably the brain isolate.

Spread of herpes simplex virus type-1 (Miyama +GC strain) to the central nervous system after intraperitoneal inoculation: the role of the myenteric plexus of the gut

The pathways taken by the HSV-1 virus after intraperitoneal (i.p.) inoculation were studied in 5-week old male C3H/HeN mice injected with 1 x 10(4) PFU (100 LD50) or 5 x 10(5) PFU (5000 LD50) of HSV-1 (Miyama +GC strain). At the higher dosage (5 x 10(5) PFU), HSV-1 began replicating in the adrenal from the first day, then in the gut and thoracic portion of the spinal cord by the third day, and in the brainstem by the fourth day, as shown by the titers of the virus in these organs. By immunoperoxidase staining HSV-1 was localized in a necrotic area of the adrenal, the myenteric plexus of the gut, the intermediolateral columns of the thoracic cord, and the vagus nerve nuclei of the medulla oblongata. In the low dose mice (1 x 10(4) PFU), HSV-1 was not isolated from the adrenal or thoracic segment of the spinal cord from the time of inoculation until the time of death. It was, however, isolated from the gut on days 4-6 and from the brainstem by day 5. HSV-1 was never isolated from the blood of either group at any time. The localizations of viral replication suggest that in the mice inoculated with 1 x 10(4) PFU, HSV-1 spreads to the brainstem via the vagal nerves after replication in the myenteric plexus of the gut. In the mice given the higher dose, localizations suggest not only the above route, but also that the virus spread to the intermediolateral columns of the spinal cord after replicating in the adrenal.